01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Work-related asthma is an umbrella covering occupational asthma and work-exacerbated asthma. Sensitiser-induced occupational asthma follows immune sensitisation to agents such as flour and enzymes, laboratory animals, wood dust, isocyanates or other chemicals; symptoms may begin only after months or years. Irritant-induced disease follows one or more substantial irritant exposures and does not require sensitisation. A job title alone is insufficient: cleaners, healthcare workers, bakers, paint sprayers and manufacturers may each encounter several different agents and tasks.
The core diagnostic reasoning has two axes. First establish asthma objectively, ideally before escalating inhaled corticosteroid obscures variability. Then demonstrate a reproducible relationship between airway change and work. A single clinic spirometry result cannot do both. Specialist-interpreted serial PEF across representative work and rest periods is pragmatic, while specific IgE or skin testing can support sensitisation to selected agents but does not alone prove occupational asthma.
Management combines ordinary evidence-based asthma care with prevention of further causal exposure. Early complete avoidance after sensitiser-induced disease offers the best chance of improvement, although asthma can persist. Exposure reduction may be insufficient and must be assessed by occupational experts. Employment decisions should be shared, confidential and documented, involving occupational health, the employer with consent, safety representatives and benefits or legal advice where appropriate.
Key points
- Ask every working-age adult with new or deteriorating asthma what they do, which agents they handle, whether symptoms change across shifts and whether colleagues are affected.
- Occupational asthma means new asthma caused by work; work-exacerbated asthma is pre-existing or coincidental asthma made worse by workplace conditions, and the distinction affects prevention and prognosis.
- Sensitiser-induced disease often follows a symptom-free latency period, whereas irritant-induced asthma may follow a substantial exposure without allergic sensitisation.
- Improvement on rest days or holidays supports a work relationship but is not diagnostic because treatment, infections and exposure patterns also change.
- Arrange early specialist occupational-respiratory assessment; delay can allow continued injury and may erase the chance to demonstrate an exposure-response pattern.
- Serial peak expiratory flow is most informative while the person is still in the relevant work, provided continued exposure is clinically safe.
- Do not advise abrupt resignation as a diagnostic strategy; health, income, legal rights and safer redeployment must be considered with informed specialist support.
- Exposure control is disease-modifying. Inhalers reduce inflammation and symptoms but do not make continued uncontrolled exposure safe.
- Communicate with an employer or occupational-health service only with the person's informed consent, except where a separate overriding legal duty has been established and explained.
- Local reporting, occupational-disease and workplace safety duties vary across UK jurisdictions and roles; use current HSE or devolved guidance and specialist advice.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
High-molecular-weight sensitisers
Flour, laboratory animals, enzymes and other biological proteins can produce an IgE-associated sensitisation after a symptom-free latent period.
Low-molecular-weight chemicals
Isocyanates, persulfates, metals and other reactive chemicals cause sensitiser-induced asthma through varied immune and cellular mechanisms.
Irritant-induced asthma
A substantial single exposure or repeated lower-level irritant exposure can cause persistent variable airway disease without a classic sensitisation latency.
Work-exacerbated asthma
Dust, fumes, exertion, cold or stress at work may aggravate pre-existing asthma without the workplace having caused the underlying disease.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Workplace airway exposure
An airborne sensitiser or irritant deposits on bronchial epithelium during specific tasks, often at concentrations not reflected by job title alone.
- 2Sensitisation or epithelial injury
Adaptive immune responses develop to a sensitiser, or direct irritant damage activates innate inflammatory and neural pathways.
- 3Variable bronchoconstriction
Re-exposure provokes smooth-muscle contraction, mucosal swelling and mucus, causing work-related changes in symptoms and expiratory flow.
- 4Persistent disease
Continued exposure sustains inflammation and remodelling, so symptoms may stop following the work schedule and persist even after removal.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
New variable cough, wheeze, chest tightness or breathlessness after a latency period in a job with a recognised respiratory sensitiser, often worsening during work blocks and improving on longer periods away.
Asthma begins after a clearly described high-level irritant event or repeated substantial irritant exposures, without a sensitisation latency pattern. Document the event, co-workers, emergency attendance and exposure controls precisely.
Established asthma deteriorates with dust, fumes, cold air, exertion, cleaning products or poor workplace control, but evidence does not support new sensitiser-caused disease. Exposure reduction remains important even when classification differs.
Rapid worsening, attacks requiring urgent care, a major spill, inadequate respiratory protection or several affected workers makes continued workplace challenge unsafe and requires immediate exposure removal and specialist coordination.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Detailed job, task and exposure chronologyFirst step - Why
- Identify plausible agents and the temporal disease pattern.
- Interpretation and limitations
- Record every job, task, product, dust, aerosol, fume, protective control, symptom-free latency and change across shifts, weekends and holidays. Safety data sheets help identify ingredients but do not exclude unlisted sensitisation.
- 02
Quality-assured spirometry with bronchodilator reversibility - Why
- Demonstrate variable airflow obstruction and identify fixed disease.
- Interpretation and limitations
- A compatible change supports asthma but a normal test between episodes does not exclude it. Persistent obstruction broadens the differential; ensure testing is safe and record recent bronchodilator and corticosteroid treatment.
- 03
Serial peak expiratory flow at work and away - Why
- Demonstrate repeated physiological association with workplace exposure.
- Interpretation and limitations
- Use a specialist-agreed schedule with multiple daily readings, work tasks, treatment and symptoms recorded over representative periods. Expert or validated computer interpretation is preferable; falsification, poor technique and non-work confounders must be considered without assuming bad faith.
- 04
FeNO and blood eosinophil count - Why
- Characterise type 2 airway inflammation in diagnostic context.
- Interpretation and limitations
- Raised values support eosinophilic inflammation but do not identify its occupational cause. Normal values, especially after inhaled or oral corticosteroid exposure, do not exclude asthma or occupational disease.
- 05
Specific IgE or skin-prick testing to a relevant agent - Why
- Support sensitisation where a validated allergen test exists.
- Interpretation and limitations
- A positive test documents sensitisation, not necessarily disease; a negative test may be unhelpful for low-molecular-weight chemicals or poorly standardised extracts. Interpret with exposure and physiological work association.
- 06
Specialist bronchial or specific inhalation challenge - Why
- Resolve selected cases when usual evidence remains insufficient.
- Interpretation and limitations
- Non-specific bronchial challenge tests airway hyperresponsiveness but not occupational causation. Specific inhalation challenge is available only in expert centres and requires stringent safety and exposure methods; it is not a routine workplace experiment.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Work-exacerbated asthma
Established asthma predating the job and worsening with non-specific workplace conditions suggests aggravation rather than new sensitiser-caused disease.
Inducible laryngeal obstruction
Abrupt inspiratory noise and throat tightness during irritant exposure with dynamic laryngeal closure differs from lower-airway obstruction.
Occupational rhinitis
Nasal symptoms may precede or accompany asthma but can also occur alone; objective lower-airway variability is needed for an asthma diagnosis.
Hypersensitivity pneumonitis
Systemic symptoms, inspiratory crackles, restriction and diffuse exposure-related imaging change indicate parenchymal immune disease rather than isolated asthma.
Dysfunctional breathing
Workplace stress can trigger disproportionate dyspnoea without objective airflow change, but this should not be assumed before exposure-related disease is investigated.
Additional chapter-specific clues
Fever, systemic upset, inspiratory crackles, reduced gas transfer, focal imaging, fixed obstruction or progressive breathlessness should prompt consideration of hypersensitivity pneumonitis, silicosis, COPD, infection, bronchiolitis or another occupational disorder.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01First reviewAsk beyond the job titleFirst stepAdult-onset asthma, unexplained deterioration or symptoms linked to work.+
- 1List current and past jobs, then break each job into tasks, products, airborne agents, spills, ventilation, respiratory protection and affected colleagues.
- 2Build a calendar of symptom onset, latency, shift timing, weekends, holidays, sick leave, treatment changes and major exposure events.
- 3Assess current asthma severity and immediate exposure safety, provide an action plan, and arrange objective asthma testing without delaying urgent treatment.
- 4Refer early to a clinician experienced in occupational asthma while exposure-response measurements remain feasible and employment advice can be coordinated.
02Objective linkTest work association safelyAsthma is suspected and the person remains in potentially relevant employment.+
- 1Agree with the specialist whether continued exposure is safe; severe attacks or a hazardous acute exposure require removal rather than deliberate re-challenge.
- 2Teach and check PEF technique, then collect multiple daily readings with task, location, symptoms and inhaler use across work and comparable away periods.
- 3Perform quality-assured spirometry and the current asthma objective-test sequence; add agent-specific sensitisation tests only when biologically and technically appropriate.
- 4Have the record interpreted by an occupational respiratory specialist, integrating physiology with exposure chronology rather than relying on a visual weekday pattern alone.
03Confirmed or likelyProtect lungs and livelihoodEvidence supports occupational asthma or a dangerous workplace relationship.+
- 1Explain diagnosis, prognosis and uncertainty to the person first, including why continuing causal exposure may worsen long-term asthma even when inhalers suppress symptoms.
- 2With informed consent, engage occupational health and the employer to pursue elimination, substitution, engineering control or genuinely non-exposed redeployment; respiratory protective equipment is not the sole control.
- 3Optimise guideline-based asthma treatment, inhaler technique, adherence and action planning, then monitor recovery after exposure change using symptoms, exacerbations and lung function.
- 4Discuss jurisdiction-specific reporting, compensation, union or legal advice and psychosocial support without presenting the treating clinician as an employment-law decision maker.
04Uncertain resultReassess rather than erase the historyInitial tests are normal, discordant or collected after exposure has ended.+
- 1Check whether treatment, leave from work, poor technique or an unrepresentative production period reduced the chance of detecting variability.
- 2Reconsider asthma mimics and other occupational lung diseases with full spirometry, imaging or gas transfer testing guided by the phenotype.
- 3Seek specialist interpretation before declaring the disease non-occupational, particularly when a plausible sensitiser and strong temporal history remain.
- 4Avoid unsafe unsupervised return to exposure solely to make the diagnosis; agree a risk-managed plan with occupational and respiratory expertise.
Key medicines and prescribing safety3 treatments · regimens, roles and cautions+
Low-dose inhaled corticosteroid-formoterol anti-inflammatory reliever
For eligible people aged twelve and over, use the exact inhaler and as-needed regimen specified by NICE and the local formulary after technique training.Confirm the device is licensed for the intended AIR or MART regimen and provide a personalised action plan. Increasing use signals poor control or ongoing exposure; inhaled treatment does not neutralise a causal workplace sensitiser.
Maintenance inhaled corticosteroid-formoterol MART regimen
Use the locally selected low- or moderate-dose maintenance schedule with the same inhaler as reliever, following NICE steps and product limits.Check adherence, technique, triggers and diagnosis before escalation. Device strengths and maximum inhalations differ; repeated oral corticosteroid need or continuing work-related attacks requires specialist review and exposure intervention, not automatic dose escalation alone.
Short-acting beta2 agonist rescue inhaler
Use the prescribed inhaled dose for breakthrough symptoms only within an asthma plan that also provides inhaled corticosteroid treatment.Do not use SABA as the only asthma treatment. Increasing reliance, reduced duration of benefit or workplace-preventive dosing that hides recurrent exposure-related symptoms requires urgent control review and may require emergency assessment.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Persistent asthma
Delayed recognition and ongoing sensitiser exposure can leave chronic symptoms and hyperresponsiveness even after the worker changes role.
Severe exacerbation
A high or unexpected workplace exposure may provoke dangerous bronchoconstriction and respiratory failure, with severity determined by its extent and the patient's underlying reserve.
Fixed airflow limitation
Repeated inflammation and remodelling can make obstruction less reversible and reduce long-term respiratory reserve, adding morbidity beyond the initial pulmonary disorder.
Employment and financial harm
Exposure avoidance may require redeployment or leaving work, creating income, identity and legal consequences that need confidential specialist support.
Coworker exposure
Failure to identify a causal agent may leave other employees at risk of sensitisation and preventable disease.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- During diagnostic recording, review PEF technique, completeness, work tasks, exposure changes and reliever use rather than accepting an uninterpretable diary at the end.
- Track validated symptom or control score, night waking, work and non-work limitation, reliever use, attacks, oral corticosteroid courses and unscheduled care.
- Repeat spirometry after exposure removal or redeployment to document trajectory; improvement may be incomplete and absence of rapid normalisation does not refute causation.
- Review whether agreed workplace controls actually remove the relevant exposure, with occupational-hygiene input rather than relying solely on self-reported mask use.
- Monitor employment, income, mood and treatment burden because an apparently successful clinical recommendation can cause major social harm if poorly coordinated.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Latency separates mechanisms
Sensitiser-induced disease usually requires a latency period, while a well-documented major irritant exposure can cause asthma without sensitisation. Neither mechanism is proven by timing alone.
Holidays are natural experiments
Recovery during a longer holiday can be more revealing than a weekend, but concurrent infections, seasonal allergen change and altered treatment mean the pattern still needs objective confirmation.
Sensitisation is not causation
Specific IgE can show immune recognition of a workplace allergen while the asthma has another cause. Pair immunology with asthma physiology and a credible exposure-response relationship.
Removal may not cure
Airway hyperresponsiveness can persist after exposure stops, particularly after diagnostic delay. Persistent asthma does not disprove occupational causation and still needs long-term treatment.
Consent protects trust
The employer may need information to control risk, but clinical details should not be shared casually. Agree what is disclosed, to whom and for what purpose with the worker.
11Common pitfallsFrequent interpretation and management errors.
- 01
Writing 'works in a factory' without identifying tasks, agents, controls, temporal pattern or co-worker illness.
- 02
Telling a person to leave employment immediately when the situation permits safer specialist assessment and coordinated redeployment.
- 03
Waiting until months after exposure has ended before attempting work-related physiological measurements.
- 04
Using one positive specific IgE result as proof that the workplace agent caused asthma.
- 05
Treating escalating symptoms only with more inhaler therapy while uncontrolled causal exposure continues.
- 06
Sharing a suspected diagnosis with the employer without informed consent or considering the worker's social and legal position.